The Latin phrase ceteris paribus means “all else being equal.” It refers to a situation where two or more things are being compared or a relationship is being explored and the speaker wants to simplify the discussion, for clarity. It is most commonly used in economics, although it can also come up in philosophy and may also be employed in a court of law when a person wishes to make a particular kind of argument.
When people make a ceteris paribus assumption, they ask that people assume, for the sake of argument, that all of the factors except one in a situation will remain the same. Someone might say “when the price of employing domestic workers falls, ceteris paribus, more people will hire maids.” In this situation, the person is saying that, assuming no other factors that might influence the reasons people decide to hire domestic workers are involved, a fall in labor prices will result in an uptick in employment.
Events rarely occur in isolation and it is unusual to have a situation where people can in fact assume that all else would be equal, but making an argument ceteris paribus can allow someone to get a point across and may be the starting point for a deeper discussion. Like other positions taken for the sake of simplicity or argument, the speaker recognizes that the hypothetical conditions are not very realistic, but wants to assume that they are in order to facilitate a conversation.
In legal settings, people sometimes use this argument when they are comparing scenarios. Either side of a case can make an argument with two or more hypotheticals, asking the judge and jury to think about how different situations would play out, ceteris paribus. Theoretical arguments of this nature are common in the law, where people want to present judges and juries with plausible explanations for a series of events and to explore possibilities without firmly committing to anything.
When an attorney presents a hypothetical situation, the attorney stresses that certain assumptions are being made solely for the purpose of hypothetical discussion. No admissions are being made and the attorney's comments cannot be used against the client. Someone might say, for example, “let's assume for the sake of argument that my client did kill the deceased. How do you think a woman of small build and minimal strength might have strangled a heavyset man?” In this case, the attorney isn't saying that the client did kill anyone, but is asking the jury to think about how someone might have been killed, given the obvious constraints.